Fullerenes, such as carbon nanotubes, graphene, fullerenes (such as C60, C70, C76, C78, C80, C82, C84 and C90), and polycyclic aromatic hydrocarbons have attractive features such as high strength and high heat conductivity and electrical conductivity. Covalent modifications to the fine structure of the fullerenes interfere with their attractive strength- and conductivity characteristics. Therefore, covalent anchoring of fullerenes in a composite is sometimes not advantageous; in these cases, it is preferable to anchor the fullerenes by non-covalent association with the polymer.
Preparation of Fullerene-Binding Ligand Capable of Becoming Incorporated in the PE Polymer, or Incorporated as Side Chains to the PE Polymer.
Compound 9A-1: Phenanthrene, a CNT-binding ligand, is here modified in order to become attached as a sidechain to the PE polymer. Compound 9A-1, a phenanthrene derivative carrying an octene ring at a position that does not interfere significantly with the binding of the Phenanthrene moiety to the CNT, is prepared by for example reacting ethyl phenanthrene-9-carboxylate with (Z)-cyclooct-4-en-1-ylmethanol in a transesterification reaction. The synthesis is shown in FIG. 9A-1.
Compound 9A-2a: Pyrene, a CNT- and graphene-binding ligand, is here modified to form a dimer of pyrene, capable of becoming attached as a sidechain to the PE polymer, thereby linking two PE polymers. The Compound 9A-2a is prepared by a route inspired by Tetrahedron Letters, 52(47), 6284-6287, where the starting material is (6-bromo-3,8-dibutylpyren-1-yl)trimethylsilane. This compound is reacted with a di-boronic acid, with an example shown in FIG. 9A-2 in a Suzuki coupling, thereby linking two pyrene units together. Subsequently, the bromine funcationalities are converted into carboxylic acids by reacting with butyllithium and carbondioxide. An esterifaction with (Z)-cyclooct-4-en-1-ylmethanol results in di-pyrene moiety that can be polymerized into a polyethylene by reaction with for example Grubb's 2nd generation catalysts followed by hydrogenation. A variety of different di-boronic acids can be used as linkers between the two pyrene moieties. Examples includes (ethyne-1,2-diylbis(4,1-phenylene))diboronic acid or other molecules with alternating triple bonds and benzene rings end-capped with benzenes functionalized with boronic acids. Some examples are shown in FIG. 9A-2.
The synthesis is shown in FIG. 9A-2.
Compound 9A-3: The SWNT-binding peptide GSSGSSPQAQDVELPQELQDQHREVEV-GSSGSS, is here modified in order to become attached as a sidechain to the PE polymer. The peptide derivative is prepared by clasical solid phase chemistry for preparing peptides: The synthesis can be carried out using standard FMOC-based solid phase synthesis using for example a Rink amide MBHA resin and automated synthesis. FMOC deprotection can be done using 20% 4-methylpiperidine in DMF and the amino acid couplings can be done with HBTU and DIPEA. The final peptide sequence can then be cleaved from the resin using a mixture of TFA, water and TIPS. Where needed, standard protection group chemistry was employed. The said peptide can then be polymerized with cyclooctene as the co-monomer and Grubbs' 2nd generation catalyst as shown in FIG. 9A-3. Subsequently, the double bonds can be hydrogenated under suitable conditions such that the peptide bonds are not cleaved; the result is a polyethylene type polymer derivative with CNT binding peptide sequences.
Compound 9A-4b: The CNT-binding and graphene-binding ligand pyrene is here modified to become incorporated in the PE polymer. The pyrene derivative is prepared by reacting pyrene-1-carboxylic acid with (Z)-cyclooct-4-en-1-ylmethanol in an esterification reaction. This derivative can then be polymerized in a ring-opening methathesis polymerization reaction using for example Grubbs' 211d generation catalyst and cyclooctene. Subsequent hydrogenation leaves a polyethylene grafted with pyrene moieties.
Compound 9A-5: The CNT-binding ligand Anthracene is here linked, via a relatively long linker, to cyclococtene as shown in FIG. 9A-5, where n can be any number from 0 to 100. The synthesis of this compound follows the previously outlined synthesis but the acid chloride is in this case reacted with (Z)-cyclooct-4-en-1-ylmethanol. Polymerization using the ROMP methodology outlined previously with cyclooctene as the co-mononer results in an unsaturated polymer, where the spacing between the anthracene moieties in the polymer chain can vary. For example, two of the cyclooctene containing 9,10-dihydroanthracene derivatives can be reacted with each other in the ROMP reaction thus giving a comparatively short distance between two 9,10-dihydroanthracene molecules.
Preparation of Fullerene/PE Composites with Attractive Characteristics.
The PE composites are produced, by i) performing the polymerization, and then ii) reducing the double bonds of the polymer (e.g by hydrogenation). Thereafter, as a final processing step, the solvent may be removed (e.g. by evaporation), in which case the composite may have been made in a casting mould (in situ polymerization). Alternatively, the composite material, present at this step in solvent, may be processed as described in the paragraph “Processing of fullerene/PE composites” below.
Composites Comprising Compound 9A-1.
Compound 9A-1 may be used to prepare a CNT/PE composite, in which SE1 is a CNT, Ligand1 is Phenanthrene, Ligand 2 is an ester linkage, and SE2 is a polyethylene. The synthesis is depicted in FIG. 9B-1, and involves the following synthetic steps:                i) Polymerization using Grubbs' 2nd Generation catalyst, at a temperature between 20 and 140° C. under oxygen-free conditions, i.e. solvents have undergone freeze-pump-thaw cycles and the reaction is run under an argon atmosphere. CNTs are dispersed in an appropriate solvent, such as toluene, xylene, tetrahydrofurane, dichloromethane or other inert halogenated solvents (optionally mediated by sonication). Compound 9A-1 (at a molar excess to CNT of e.g. 100-10,000-fold), and Octene (at a molar ratio of 0.01 to 100,000 relative to Compound 9A-1 of between 5 and 100), are added to the CNT dispersion together with Grubbs' 2nd Generation catalyst. Polymerization is allowed to proceed until insignificant new polymer is generated, and is then terminated by quenching the reaction mixture with methanol precipitating the polymer, which is then isolated by filtration and dried.        ii) Reduction of double bonds, e.g. by hydrogenation is done by dispersing the isolated unsaturated polymer in a suitable solvent such as xylene, tetrahydrofurane, toluene or halogenated solvents. Hydrogenation can be done with hydrogen gas in a pressurized reactor and employing a suitable catalyst such as Pd/C. Another example is to use tosyl hydrazine and trimethylamine.        
Composites Comprising Compound 9A-2.
Compound 9A-2 may be used to prepare a graphene/PE composite, in which SE1 is graphene, Ligand1 is a pyrene dimer, Ligand2 is a carbon-carbon bond, and SE2 is a PE polymer. Alternatively, the CMU employed can also be considered to involve a SE1 which is a PE polymer, a Ligand1 which is a carbon-carbon bond, a linker which comprises the pyrene dimer, a Ligand2 which is a carbon-carbon bond, and a SE2 which is a PE polymer. The synthesis is depicted in FIG. 9B-2, and involves the following steps:                i) Polymerization. Compound 9A-2 and cyclooctene is mixed with graphene (5 wt % of graphene and 95 wt % of Compound 9A-2 and cyclooctene) in an appropriate solvent such as benzene, toluene, xylene, halogenated solvents such as dichloromethane, tetrachloroethane, and chlorbenzene. Optionally, sonication is employed to better disperse the graphene. After the Compound 9A-2 has been allowed to bind to the graphene the polymerization is started by adding a catalyst such as Grubbs' 2nd generation catalyst or other suitable Ruthenium catalysts. Polymerization is allowed to proceed until a suitable molecular weight is obtained. The reaction mixture is then quenched with methanol, which will precipitate the unsaturated polymer thathas graphene bounded.        ii) Reduction of double bonds, e.g. by hydrogenation is done by dispersing the isolated unsaturated polymer in a suitable solvent such as xylene, tetrahydrofurane, toluene or halogenated solvents. Hydrogenation can be done with for example hydrogen gas in a pressurized reactor and employing a suitable catalyst such as Pd/C. Another example is to use tosyl hydrazine and trimethylamine.        
Composites Comprising Compound 9A-3.
Compound 9A-3 may be used to prepare a CNT/PE composite, in which SE1 is a CNT, Ligand1 is a polypeptide, the linker is a 3a,4,7,7a-tetrahydro-1H-4,7-methanoisoindole-1,3(2H)-dione, Ligand2 is a carbon-carbon bond, and SE2 is a polyethylene polymer. The synthesis is described in FIG. 9B-3, and involves the following steps:                i) Polymerization. Compound 9A-3, at a concentration of e.g.1-100 mM is first mixed with CNT (at a concentration resulting in a final concentration in the composite of 10 wt %), in an appropriate solvent such as benzene, toluene, xylenes, and halogenated solvents such as dichloromethane, tetrachloroethane, and chlorbenzene. Optionally, sonication is employed to better disperse the CNT. After Compound 9A-3 has been allowed to bind to the CNT, a polyethylene precursor such as cyclooctene is added at a molar ratio of 0.01 to 100.000, together with the catalyst such as Grubbs' first Ruthenium, dichloro(phenylmethylene)bis(tricyclohexylphosphine)), second Ruthenium, [1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylideneldichloro (phenylmethylene)(tricyclohexylphosphine)) or third generation catalyst or the Hoveyda-Grubbs catalyst (Ruthenium, [1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro[[2,-(1-methylethoxy)phenyl]methylene], [1,3-Bis(2-methylphenyl)-2-imidazolidinylidene]dichloro(2-isopropoxyphenylmethylene)ruthenium(II), 1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro[3-(2-pyridinyl-κN)propylidene-κC]ruthenium(II), [1,3-Bis(2-methylphenyl)-2-imidazolidinylidene]dichloro(benzylidene) (tricyclohexylphosphine)ruthenium(II), Dichloro(3-methyl-2-butenylidene)bis(tricyclohexylphosphine)ruthenium(II), [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(3-methyl-2-butenylidene) (tricyclohexylphosphine)ruthenium(II), [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(benzylidene)bis(3-bromopyridine)ruthenium(II)). Polymerization is allowed to proceed until insignificant new polymer is generated, and is then terminated by quenching with methanol and isolating the precipitated polymer by filtration.        ii) Reduction of double bonds, e.g. by hydrogenation is done by dispersing the isolated unsaturated polymer in a suitable solvent such as xylene, tetrahydrofurane, toluene or halogenated solvents. Hydrogenation can be done with for example hydrogen gas in a pressurized reactor and employing a suitable catalyst such as Pd/C. Another example is to use tosyl hydrazine and trimethylamine.        
Composites Comprising Compound 9A-4a.
Compound 9A-4a may be used to prepare a CNT/PE composite, in which SE1 is a CNT, Ligand1 is a pyrene, the linker comprises an ester bond, Ligand2 is a carbon-carbon bond, and SE2 is a polyethylene polymer. In fact, two SE2 are linked to each pyrene. The synthesis is described in FIG. 9B-4, and involves the following steps:                i) Polymerization. Compound 9A-4a, at a concentration of e.g. 1-100 mM is first mixed with CNT (at a concentration resulting in a final concentration in the composite of 0.1; 1; or 10 wt %), in an appropriate solvent such as benzene, toluene, xylene, or halogenated solvents such as dichloromethane, tetrachloroethane, and chlorbenzene. Optionally, sonication is employed to better disperse the CNTs. After Compound 9A-4a has been allowed to bind to the CNT, a polyethylene precursor such as cyclooctene is added at a concentration of 1-100 mM together with a catalyst such as Grubbs' first Ruthenium,dichloro(phenylmethylene)bis(tricyclohexylphosphine)), second (Ruthenium, [1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro (phenylmethylene)(tricyclohexylphosphine), or third generation catalyst or the Hoveyda-Grubbs catalyst (Ruthenium, [1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro[[2,-(1-methylethoxy)phenyl]methylene], [1,3-Bis(2-methylphenyl)-2-imidazolidinylidene]dichloro(2-isopropoxyphenylmethylene)ruthenium(II), 1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylideneldichloro[3-(2-pyridinyl-κN)propylidene-κC]ruthenium(II), [1,3-Bis(2-methylphenyl)-2-imidazolidinylidene]dichloro(benzylidene) (tricyclohexylphosphine)ruthenium(II), Dichloro(3-methyl-2-butenylidene)bis(tricyclohexylphosphine)ruthenium(II), [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(3-methyl-2-butenylidene) (tricyclohexylphosphine)ruthenium(II), [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(benzylidene)bis(3-bromopyridine)ruthenium(II)). Polymerization is allowed to proceed until insignificant new polymer is generated, and is then terminated by quenching with methanol and isolating the precipitated polymer by filtration.        ii) Reduction, e.g. by hydrogenation is done by dispersing the isolated unsaturated polymer in a suitable solvent such as xylene, tetrahydrofurane, toluene or halogenated solvents. Hydrogenation can be done with for example hydrogen gas in a pressurized reactor and employing a suitable catalyst such as Pd/C. Another example is to use tosyl hydrazine and trimethylamine.        
Composites Comprising Compound 9A-5.
Compound 9A-5 may be used to prepare a CNT/PE composite, in which SE1 is a CNT, Ligand1 is an anthracene, the linker is a long linker and comprises a short stretch of polyethylene, Ligand2 is an anthracene, and SE2 is a CNT. The synthesis is shown in FIG. 9B-5, and involves the following steps:                i) Linkage of two or more Compound 9A-5 molecules. Compound 9A-5, at a concentration of e.g. 1-100 mM is first mixed with CNT (at a concentration resulting in a final concentration in the composite of 0.1; 1; or 10 wt %), in an appropriate solvent such as benzene, toluene, xylene, or halogenated solvents such as dichloromethane, tetrachloroethane, and chlorbenzene. Optionally, sonication is employed to better disperse the CNTs. After Compound 9A-5 has been allowed to bind to the CNT, Grubbs' 2nd generation catalyst is added to promote the reaction of two octenes of two compound 9A-5 molecules. If said two Compound 9A-5 molecules were bound to two different CNTs, this effectively cross-links the two CNTs. Therefore, after an appropriate time of cross-linking, a network of cross-linked CNTs will have formed.        ii) Polymerization. A polyethylene precursor such as cyclococtene is added at a concentration of 1-100 mM, together with a catalyst such as Grubbs' first Ruthenium,dichloro(phenylmethylene)bis(tricyclohexylphosphine)), second (Ruthenium, [1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro (phenylmethylene)(tricyclohexylphosphine), or third generation catalyst or the Hoveyda-Grubbs catalyst (Ruthenium, [1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro[[2-(1-methylethoxy)phenyl]methylene], [1,3-Bis(2-methylphenyl)-2-imidazolidinylidene]dichloro(2-isopropoxyphenylmethylene)ruthenium(II), 1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylideneldichloro[3-(2-pyridinyl-κN)propylidene-κC]ruthenium(II), [1,3-Bis(2-methylphenyl)-2-imidazolidinylidene]dichloro(benzylidene) (tricyclohexylphosphine)ruthenium(II), Dichloro(3-methyl-2-butenylidene)bis(tricyclohexylphosphine)ruthenium(II), [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(3-methyl-2-butenylidene) (tricyclohexylphosphine)ruthenium(II), [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(benzylidene)bis(3-bromopyridine)ruthenium(II)) [**CHR]. Polymerization is allowed to proceed until insignificant new polymer is generated, and is then terminated by quenching with methanol and isolating the precipitated polymer by filtration. Some of the polymers will have formed independently of Compound 9A-5, and some of the polymers will have become attached to the linker connecting two anthracenes.        iii) Reduction, e.g. by hydrogenation is done by dispersing the isolated unsaturated polymer in a suitable solvent such as xylene, tetrahydrofurane, toluene or or halogenated solvents. Hydrogenation can be done with for example hydrogen gas in a pressurized reactor and employing a suitable catalyst such as Pd/C. Another example is to use tosyl hydrazine and trimethylamine.        
General Comments to the Polymerization and Reduction Reactions Described Above, Leading to PE Composites.
Alternative PE precursors may be used in any of the polymerization reactions described in this example, e.g. cyclooctadiene, cyclooctatriene and cyclooctatetraene.
Depending on the relative amount of the fullerene-binding compound (i.e. Compound 9A-1, -2, -3, -4 or -5) and octene, the PE may be bound (through a fullerene-binding ligand) to the CNT at many or just a few positions along the CNT.
The production of polyethylene may lead to low density, medium density or high density polyethylene, depending on the polymerization conditions. Furthermore, by including additional precursors for the polymerization reaction such as octyl-cyclooctene or other alkyl substituted cyclooctenes as the precursors, branching of the PE may be obtained similar to branching in polyethylenes obtained from Ziegler-Natta type polymerizations.
Processing of the Fullerene/PE Composites Produced in this Example.
The composites produced above in this example may have been formed in a cast mould, and if desired the solvent can simply be evaporated off the composite. Alternatively, further means of processing may include any of the following:                i) Dissolve in solvent. The formed composite may be dissolved in appropriate solvent and recast in a mould. The solvent is allowed to evaporate at room temperature and under ambient pressure thus leaving the composite material having taken the desired shape in the form.        ii) Melt by heating. Melt by heating in for example an extrusion, co-extrusion, fiber-spinning, molding, ram-molding, injection molding or sintering process.        iii) Melt by heating and physical impact such as for example ram-molding.        